1. Field of the Invention
The present invention relates to a system and method of providing a Push To All (PTA) service.
2. Description of the Related Art
A Push To All (PTA) service based on an IP-based Multimedia Subsystem (IMS) includes a Push To Talk (PTT) service providing only a voice service, a Push To Video (PTV) service providing voice and image services, and a Message Session Relay Protocol (MSRP) service providing Short Message Service (SMS) or binary data service.
The PTA is based on Session Initiation Protocol (SIP), which is a text-based application level protocol, and SIP is adopted by many systems due to its simple structure and excellent extendibility compared to other protocols. Literally, the SIP is a signaling protocol used to connect a session. The SIP can be used in a video telephone call, multimedia, connecting to an online game, etc., in addition to an Internet telephone call. RFC 2543 is a first version of an RFC that was adopted as a standard, and has been updated to RFC 3261.
When a PTA service subscriber wants to communicate with a counterpart, the subscriber selects the counterpart to invite, generates an invitation message in SIP format, and transmits the message to a server by selecting a call button or a service start button on a PTA terminal. According to this process, a session is created by the server, and the PTA subscriber participates in a PTA session such as PTT, PTV, MSRP, etc.
When another subscriber out of the PTA session requests a called subscriber, whose line is busy due to participation in the PTA session, to accept another PTA session, the server informs the called subscriber of this request, and then receives a response indicating an intention to participate in the other PTA session, thereby enabling the called subscriber to participate in two PTA talk sessions simultaneously. In other word, the PTA service provides a multi session.
The PTA service allows each PTA terminal subscriber to be provided with the multi-session after each PTA terminal subscriber registers information in advance as to whether to accept the multi session with the server.
The PTA service allows “Call-Lag” multiple management to be performed by the SIP used by the PTA service to provide the multi session.
Consequently, terminals such as mobiles, PDAs, etc., providing the PTA service perform “Call-Lag” multiple management and have limited resources left over to provide the multi session.